Functions in C

Function declarations and definitions

C uses function prototypes to declare signatures before use. This helps the compiler validate argument and return types.

#include <stdio.h>

int add(int a, int b); // prototype

int main(void) {
    printf("%d\n", add(4, 5));
    return 0;
}

int add(int a, int b) {
    return a + b;
}

Pass by value understanding

• C passes arguments by value by default.
• Use pointers when a function must modify caller data.
• Keep function responsibilities narrow and testable.